Slow Waves in Health and Disease

Motility disorders of the gastrointestinal tract increase with aging and inflammatory conditions; constipation and faecal incontinence are the most common symptoms in the elderly.

Several control systems are responsible for the regulation of normal transit of contents through the gastrointestinal tract. One of the most important involves local reflexes controlled by the enteric nervous system.

Whilst the enteric nervous system plays a major role in peristalsis, the frequency and propagation characteristics of peristaltic activity under normal conditions are governed by intrinsic, omnipresent, electrical membrane-potential oscillations often referred to as pacemaker activity or ‘slow waves’.

These slow waves are readily visible on an electrogastrogram (EGG) and have been used for diagnostic purposes in patients with dyspepsia, motility disorders or unexplained nausea and vomiting.

Interstitial cells of Cajal (ICC) generate the slow waves and appear to act as an intermediate between the enteric nervous system and smooth muscle cells.

We are interested mechanisms of drug-induced dysrhythmia leading to nausea and vomiting, and also in the changes in the control of slow waves during neurodegenerative diseases.

Radiotelemetric Recordings of the Electrogastrogram

We use radiotelemetric recording techniques to record gastric slow waves in the mouse, Suncus murinus and ferret.The approach involves the surgical implantation of radiotransmitters capable of recording gastric myoelectric signals (sampled at 1 kHz), and electronic filtering in several steps to remove
cardiac and respiratory signals, as well as low frequency artifacts such as
movement. Data can then be computed on
successive sections of recordings to reveal the dominant power (DP, the highest power in recorded range); ii) the dominant frequency (DF, frequency bin with the highest power in
the range); iii) the DF instability coefficient (DFIC, defined as
the standard deviation of the DF divided by its mean, over a 10 min period). We can then look at the duration of effects of drug action during our experiments, and also correlate the information with changes in blood pressure and temperature (also measured telemetrically), and also with behavioural changes including emesis, modification of feeding and drinking, and locomotor activity. We are in the process of advancing our technology to be able to simultaneously record respiratory function by whole body plethysmography during the acquisition of radiotelemetric data..